Oscillation generation



April 16, 1946.

H. L. MORRISON OSCILLATION GENERATION Fild Feb. 5, 1944 INVENTORHOWQBZJZ orrson ATTORN EY Patented Apr. 16, 1946 OSCILLATION GENERATIONHoward Larue Morrison, Merchantville, N. as-

signor to Radio Corporation of America, a corporation of DelawareApplication February 5, 1944, Serial No. 521,191

Claims.

The present invention relates to high frequency oscillation generationcircuits employing multigrid vacuum tubes.

Broadly stated, the invention comprises a pushpull oscillator utilizinga pair of screen grid vacuum tube electrode structures capable ofeflicient- 1y generating oscillations in the 300 megacycle region. Inorder to provide feed back between the output and input electrodes ofthe tube, there is provided a folded back one-half wavelengthtwo-conductor line, one of whose conductors couples together the inputand output electrodes of one electrode structure, while the otherparallel conductor couples together the input and output electrodes ofthe other electrode structure. The length (half wave) of the conductorsassures the desired phase reversal in the voltage at one end relative tothe other.

A more detailed description follows in conjunction with a drawing, whosesingle figure illustrates one embodiment of the invention. Although thedrawing illustrates a dual beam tetrode power tube having a pair ofscreen grid electrode structures within a single envelope, it should beunderstood that the principles of the invention are applicable to anyscreen grid tube.

Referring to the drawing, there is shown a push-pull oscillationgenerator comprising a pushpull beam power amplifier tube it of the RCA832 type. This tube is a heater-cathode type containing in one envelopetwo beam power units each including a cathode, an input grid, a screengrid and an anode, as shown. The input grids are shielded from theoutput anodes by the screen ids, and the terminals for these electrodesextend from opposite sides. of the envelope. This particular type oftube (RCA 832) is designed for use primarily as a power amplifier forultra high frequency energy, but has been adapted in the circuit hereinillustrated to function as an oscillator in the range of 300 megacycles.

The anodes are connected to one end of a tuned parallel conductor systemH which is shorted at the other end by a bridge member whose midpoint isconnected to a source of anode polarizing potential B+. A slider l2,which is a short-circuiting member adjustable in position over thelengths of the conductors of, anode line circuit ll, serves to tune theanode circuit.

Connected to the input grids is a folded-back parallel conductor linel3, which is electrically one-half wavelength long at the operatingfrequency. One end of this line is connected to the input grids whiletheother end is free and brought back to the Vicinity of the tubeenvelope in order to couple the free ends of the conductors of the linecapacitively to the anodes. It should be noted that each conductor ofline it which i coupled at one end to an input grid of one beam powerunit is capacitively coupled at its other end to the anode of the samebeam power unit. Because of the particular length of the lin I3(one-half wavelength) there is a. phase reversal in voltage at one endrelative to the other which satisfies the requirement that the gridvoltage be out-ofphase relative to the'anode voltage of the sameelectrode structure for the condition of oscillation,

The line l3 thus provides feed back externally of the vacuum tubestructure. The desired amount of feed back coupling between the anodesand. the free ends of grid line I3 located adjacent the envelope of tube[0 is obtained by suitably adjusting the distance between these freeends and tube l8. If the grid line I3 is too long physically to satisfyany rigid requirement of compactness, then this line may be shortenedphysically but have the same one-half wave electrical length byconnecting a small variable capacitor across the free ends.

A pair of grid leak resistors l 4 are connected to points of lowpotential on the grid conductors of line [3, thus'eliminating the needfor radio frequency choke coils. Because of the particular location ofthese resistors, there is no radio frequency power wasted in them.

The oscillator of the present invention described above and utilizing anRCA-832 dual tetrode beam power, was able in one experimental embodimentto deliver five watts of power at 320 megacycles. In this embodiment,the lines I l and I3 were each a pair of copper rods. The tube andcircuit lends itself to compactness, and the physical size of theequipment can be still further reduced by shortening the physical lengthof the anode line by means of a simple two-plate air condenser acrossthe conductors thereof near the anode electrode terminals.

What is claimed is:

1. An oscillation generator comprising a vacuum tube having within anenvelope a cathode for supplying an electron stream, a first grid, a

screen grid and an anode, said screen grid shielding said first gridfrom said anode, an output tuned circuit coupled to said anode, a feedback circuit comprising a conductor one-half wavelength long connectedat one end to said first grid and folded so that its other end isoutside and adjacent said envelope at thelocation of said anode andcapacitively coupled to said anode solely by virtue of the space betweensaid last end of said line and said anode.

2. A push-pull oscillation generator comprising a pair of electrodestructures each including a control grid and an anode, a two-conductorline which is one-half wavelength long electricall and connected at oneend to said control grids and capacitively coupled at the other end tosaid anodes primarily by virtue, of the spacing between said anodes andsaid last end of the line, said line being folded back on itself and soarranged that each conductor thereof which is connected at one end tothe control grid of one electrode structure is folded back so that itsother end is adjacent the anode of the same electrode structure forcapacitive coupling thereto, and an output tuned circuit coupled to saidanodes.

3. A push-pull oscillation generator comprising a dual electrodestructure within a single envelope, each of said electrode structuresincluding a control grid and an anode having terminals extending fromopposite sides of the envelope, an

anode tuned circuit coupled to said anodes, and

a feed back circuit comprising .a two-conductor line one-half wavelengthlong electrically, said line being connected at one end to said controlgrids and folded so that the other end is adjacent said anodes butoutside said envelope and capacitively coupled to said anodes foroperation of said generator by virtue of the spacing between said anodesand said last end of the line.

4. A push-pull oscillation generator comprising a dual multi-gridelectrode structure within a single envelope, each of said electrodestructures including a-control grid and an anode having terminalsextending from opposite sides of the envelope, and a screen grid forshielding the control grid from the anode, an anode tuned parallelconductor circuit coupled to said anodes, and a feed back circuitcomprising a two-conductor line onehalf wavelength long electrically,said line being connected at one end to said control grids and folded sothat the other end is adjacent said anodes but outside said envelope andcapacitively coupled to said anodes for operation of said generatorprimarily by virtue of the space" between said anodes and the last endof the line, each conductor of said line having its free endcapacitively coupled to the anode of the same electrode structure towhose control grid its other end is connected. I

5. A push-pull oscillation generator comprising a dual multi-grid,electrode structure within a single envelope, each of said electrodestructures including a cathode for producing a stream of electrons, acontrol grid and an anode having terminals extending from opposite sidesof the envelope, and a screen grid shielding the control grid from theanode, an anode tuned parallel conductor circuit coupled to said anodes,and a feed back circuit comprising a two-conductor line onehalfwavelength long electrically, said line being connected at one end tosaid control grids and folded so that the other end is adjacent'to saidanodes but outside said envelope and capacitively coupled to said anodesfor operation of said generator primarily byrvirtue of the space betweensaid anodes and last end of the line, each conductor of said line havingits free end capacitively coupled to the anode of the same electrodestructure to Whose control grid its other end is connected, and separategrid leak resistors connected between points of low potential on the twoconductors of said line and the cathodes of said electrode structures. 1

6. A push-pull oscillation generator comprising a pair of multi-gridelectrode structures each including a cathode for producing an electronstream, a control grid, an anode, and a screen grid shielding thecontrol grid from the anode, a twoconductor line one-half wavelengthlong electrically connected at one end to said control grids andcapacitively coupled at the other end to said anodes primarily by virtueof th spacing between said anodes and said last end of the line, saidline being folded back on itself and so arranged that each conductorthereof which is connected at one end to a control grid of one electrodestructure has its other end adjacent the anode of the same electrodestructure, a, grid leak resistor for each conductor of said lineconnected between a point of low potential on the conductor and thecathode of that electrode structure to which the said conductor isconnected, and an output tuned circuit coupled to said anodes.

V '7. A push-pull oscillation generator comprising a pair of multi-gridelectrode structures, each including a control grid, an anode, and ascreen grid shielding the control grid from the anode, a two-conductorline having such electrical length that potentials of oppositeinstantaneous polarities appear at opposite ends thereof, said linebeing connected at one end to said control grids and capacitivelycoupled at the other end to said anodes primarily by virtue of thespacing between said anodes and said last end of the line, said linebeing folded back on itself and so arranged that the conductor which isconnected at one end to the control grid of one electrode structure hasits other end adjacent the anode of the same electrode structure.

8. Push-pull electron discharge device apparatus comprising a pair ofmulti-grid electrode, structures each including a control grid, ananode, and a screen grid shielding said control grid from the anode, atwo-conductor line one-half wave- 7 length long electrically connectedat one end to said control grids and capacitively coupled at the otherend to said anodes primarily by virtue of the spacing between saidanodes and said last end of the line, said line being folded back onitself and so arranged that each conductor thereof which is connected atone end to the control grid of one electrode structure has its other endadjacent the anode of the same electrode structure.

9. Push-pull electron discharge device apparatus comprising a pair ofmulti-grid electrode structures, each including a control grid, ananode, and a screen grid shielding said control grid from the anode, atwo-conductor line having such electrical length that potentials ofopposite instantaneous polarities appear at opposite ends thereof, saidline being connected at one end to said control grids and capacitivelycoupled at the other end to said anodes primarily by virtue of thespacing between said anodes and said last end of the line, said linebeing folded back on itself and so arranged that the conductor which isconnected at one end to the control grid of one electrode structure hasits other end adjacent the anode of the same electrode structure.

10. An oscillation generator comprising a vacuum tube having within anenvelope a cathode for producing an electron stream, a first grid, andan anode, a feed back circuit comprising a conductor having suchelectrical length that potentials of opposite instantaneou polaritiesappear at opposite ends thereof, said conductor being connected at oneend to said first grid and folded so that its other end is outside andadjacent said envelope at the location of said anode and capacitivelycoupled to said anode primarily by virtue of the space between said lastend of the line and said anode.

HOWARD LARUE MORRISON.

